1. Related Field
The present invention relates to a perfusion device for extracorporeal blood oxygenation procedures, and in particular, though not exclusively, to an integrated perfusion device for use in e.g. extracorporeal membrane oxygenation, isolated organ perfusion, isolated limb perfusion or cardiopulmonary bypass, for example, in a surgical environment.
2. Description of Related Art
Cardiopulmonary Bypass (CPB) is a technique which allows artificial maintenance of the circulation of blood and the oxygen content of the body of a patient, typically undergoing surgery. Therefore, a typical CPB apparatus performs the dual function of mechanically circulating blood and oxygenating blood while bypassing the heart and lungs during a surgical procedure.
Extracorporeal Membrane Oxygenation (ECMO) is a technique employed to support patients who are suffering from, for example, cardiopulmonary distress. ECMO is a simplified form of CPB, and is typically used in applications such as neonatal life support (e.g. for newborns with serious birth defects), or support of recipients for organ transplant.
Typical CPB and ECMO support systems consist of a number of elements which are interconnected to form the overall system. These generally comprise (a) a blood pump; (b) a blood oxygenator; (c) a heat exchanger; (d) connecting tubing; and (e) an arterial or venous reservoir. In addition to the above a number of ancillary devices are required to run these systems in the clinical setting, including a heater/cooler system for providing a cooling/heating fluid to the heat exchanger, typically pumping water through a counter-current heat exchanger positioned in either the arterial or venous lines of the perfusion system.
The heat exchanger is generally used to cool the blood and lower the patient's body temperature during surgery. However, the heat exchanger may also be used to, e.g., maintain normal body temperature, e.g. in neonatal or adult life support, or in isolated organ or limb perfusion. The heat exchanger may also be used to, e.g., heat blood in subjects suffering from hypothermia. Another application of such heat exchangers includes cardioplegic procedures. Cardioplegia, typically employed during open heart surgical procedures, involves stunning the heart by pumping a cooled mixture of blood and cardioplegic solution to the heart, in order to allow surgical procedure to be performed on the heart. The cooled mixture of blood and cardioplegic solution is typically pumped at regular intervals during the procedure. Upon completion of the procedure, the heart is brought back to normothermic temperature by pumping heated blood in a so-called “hot shot”.
Such heat exchangers are typically connected to a water circuit which relies on large mains-powered heater/cooler units. The need for a heating/cooling fluid supply and connecting tubes to/from the heat exchanger is not only cumbersome and detrimental to portability, but also presents risks of contamination associated with the presence of blood and water in the same assembly. Further, there exist obvious risks associated with the presence of mains power and water in the same circuit.
Conventional ECMO technologies employ a roller or a centrifugal pump to circulate blood through the circuit. This usually requires that the patient be positioned in an elevated position to ensure gravitation “siphoning” of venous blood into the system. Such excessive patient elevation often complicates clinical care and/or interaction with the patient during deployment.
The use of ECMO is most effectively applied if used aggressively. However, this is often hampered by the availability and complexity of the current technology and is often restricted to specialist units. The complexity of the current ECMO systems, largely involving modified conventional CPB technologies that have large surface areas of foreign materials, also tends to create relatively high blood contacting surfaces in current ECMO systems. This can lead to significant blood/biomaterial contact mediated complications, including activation of inflammatory processes, and consumption of clotting factors. Further, the relatively large priming volumes required during use of the current devices can cause a risk of haemodilution, which may be significant in the neonatal and paediatric setting where haemodilution effects are of real clinical concern.
This complexity and scale also has an impact upon clinical management, for example introducing difficulties in transporting patients for important diagnostic investigations elsewhere within the hospital, contributing significantly to the most challenging medical complications of the procedure.
European Patent Application Publication No. EP 1 624 912 (Cardiovention Inc) discloses an apparatus for oxygenating and pumping blood including a housing defining a blood flow path including, in series, a gas collection plenum, a pump space and a blood oxygenation element. A pump disposed in the pump space is configured to draw blood from the gas collection plenum and propel blood from the pump space through a heat exchanger and the blood oxygenation element. The heat exchanger includes a heat exchange plate and a coolant space.
U.S. Pat. No. 5,069,661 (Brigham and Women's Hospital) discloses a low-pressure, low blood trauma hemodynamic support system. The system may operate as a relatively static-volume, gravity-fed, extracorporeal blood circulation and oxygenation system that consists essentially of (1) a membrane-type blood oxygenator, (2) a non-occlusive roller pump, and (3) connecting tubes.
International Patent Application Publication No. WO 97/34647 (Medtronic, Inc.) discloses waterless temperature control of blood in a blood oxygenator which is achieved by providing a non-disposable heater/cooler with a temperature-controlled surface that can be intimately mated with a heat-conducting surface of a disposable blood heat exchanger associated with the oxygenator.
Japanese Patent No. JP 2006-296452 discloses a pump oxygenator comprising a Peltier unit comprising a Peltier device mounted on several heat exchangers. JP 2006-296452 discloses the use of Peltier devices to maintain temperature in a recirculation circuit. The heat exchangers comprise heat-conducting members in the form of long circular rods extending into the chamber of the heat exchange unit through which a fluid passes.
There is a need in the prior art to improve the portability and compactness of extracorporeal oxygenation devices.
There is a need in the prior art to reduce priming volumes and surface area of foreign materials in contact with blood circulated in extracorporeal oxygenation devices.
There is a need in the prior art to reduce the need for gravity drainage into such systems and provide therapeutic technology closer to the patient.
There is a need in the prior art to eliminate the need for a mains-powered heating/cooling fluid supply (typically a water supply) to control blood temperature and reduce size and improve portability of the overall assembly and mobility of a patient.
It is an object of at least one embodiment of at least one aspect of the present invention to seek to obviate or at least mitigate one or more disadvantages in the prior art.
It is an object of at least one embodiment of at least one aspect of the present invention to provide an integrated perfusion device which minimises priming volumes and surface area of foreign materials in contact with circulated blood.
It is an object of at least one embodiment of at least one aspect of the present invention to provide an integrated perfusion device which reduces the need for gravity drainage into the system.
It is an object of at least one embodiment of at least one aspect of the present invention to provide a portable, compact and integrated perfusion device which eliminates the need for a heating/cooling fluid supply (typically a water supply) to control blood temperature.